Open and close ?les for writing, C/C++ Programming

If you have computed a number (stored as a ?oating-point value) and want to display this on a plot (i.e. as a character string) you have to convert it into a STRING. That is we want to convert between the two forms:

x_number=4.367

x_string='4.367'

the ?rst is a ?oating point number (suitable for plotting or mathematical computation), and the latter is a 5-char string array (suitable for display using title or text commands, or which can be written to a ?le). For quick tasks MATLAB includes commands num2str, str2num, int2str and some others which can convert from numbers (?oating point or integer) to strings and vice versa but for best results one should learn how to use printf/scanf family of functions.

Note: One very important useage of fprintf is in program debugging. Adding in fprintf statements at crucial places in the program allows you to display the values of variables in a clean and elegant way without ?lling up the screen with numbers (which is what often happens when you simply remove the ; from the end of a line). We begin with fprintf, which outputs strings to the screen (sprintf works basically the same way but outputs data to a matlab variable, sscanf and fscanf read from strings or ?les). Here is a typical usage:>>fprintf('\nthis number %d and this one %.4f and these characters: %s\n\n',... 4,3.6,'qwerty')this number 4 and this one 3.6000 and these characters: qwerty  fprintf and sprintf take as ARGUMENTS a string containing a mix of characters and FORMAT SPECI-FIERS, followed by a number of variables (here their values are explicitly shown ). Format speci?ers begin with a '%', and end with a CONVERSION CHARACTER. There are lots of conversion characters but the ones you will use most are d for integers, e, f, and g for ?oating point numbers, and s for string data. Between the '%' and the conversion character there are various optional parameters, but most of the time you only need to use either a width (single number giving number of characters to use), and/or a precision after a decimal point (number of digits to right of '.'). If you don't specify these then MATLAB will try to do something sensible. The \n symbol represents a special 'non-printing' character - the CARRIAGE RETURN. It is non-printing because it isn't a letter or number, but it is used to say that the line has ended and the next characters will be on a new line.

Posted Date: 3/19/2013 3:23:47 AM | Location : United States







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